This invention relates to the field of charcoal briquets and other solid fuel compositions in briquets or other geometric configurations, and more particularly to the design of dimensional and geometric specifications and configurations to achieve desired lighting and burn characteristics with respect to intended uses such as barbecue cooking. The most common example of such fuel compositions are charcoal briquets which comprise comminuted char of various vegetable materials, such as wood, hulls, pits, and other agricultural waste material which is mixed with a binder and rolled, pressed or otherwise formed into briquets. However the present invention has application to other solid fuel composition, such as comminuted wood or organic material, rolled, pressed or extruded into pellets, discs, briquets or other shapes.
Charcoal briquets presently available are typically provided in a "pillow" shape which provides for reasonably satisfactory ease of manufacturing by the supplier and handling by the consumer. However, little attention has been paid to their burning characteristics as related to their shape. As is well known, such briquets are typically used for cooking on a grill or the like by preparing a multiplicity of briquets in a mounded configuration, igniting their surface by some auxilliary ignition means such as lighter fluid, electric heaters, etc., and waiting until ignition of a significant portion of the briquets has progressed until a majority of the exposed surface is ignited, and burning has progressed inwardly toward the interior of the briquet. As burning proceeds inwardly from the surface of the briquet a gray ash is formed thereon. Thus completion of the initial "ignition phase" of burning is identifiable by the formation of such visual ash on the briquet, and is defined herein as the time at which there is 60-75% visual ash formation on the briquets.
Thereafter the briquets are typically spread under a grill or the like for cooking, and they continue to burn with an intense heat throughout a "burn phase". For maximum performance of such briquets it is desirable that the ignition phase be limited in time so that the briquets may be used for cooking without undue delay, and that the burn phase be extended to provide adequate cooking time for the use intended. It is further desirable to obtain such desirable combustion performance in the most efficient manner with respect to the amount of fuel consumed. There have been very little prior art developments related to design of solid fuel articles for desired combustion performance. There has been some work at ornamental configuration of fuel briquets, as well as geometrical configuration of briquets to enhance ignition or burning by enhancing air supply, such as provision of external surface discontinuities such as ribs, flutes, groups, slots or the like, and internal openings and passages of various configurations. Such attempts may enhance commencement of ignition or overall combustion, but do not provide desired optimal ignition and burning characteristics.
Other fuel briquets intended for very rapid ignition and delivery of intense heat provided a combination of powdered metal and oxidizers in a charcoal briquet having a higher ratio of surface area to volume and/or weight. However very rapid delivery of intense heat does not provide an acceptable combustion response for cooking purposes, and such prior art suggestions have made no attempt to quantify or optimize such ratios.
Other prior art briquets have recognized that the surface area to volume ratio of the briquet may affect ignition and burn characteristics and should be increased to provide rapid ignition and burning. However, such ratios have not been employed to design a briquet providing optimal desired ignition and burning characteristics.
Accordingly, it is an object of the present invention to provide a briquet which provides desired ignition and burn phase characteristics including a maximum ignition phase of 20 minutes, followed by a sustained burn phase.
A further object of this invention to provide such a briquet with desired ignition and burn phase characteristics regardless of specific composition, raw materials, geometric shape, size, or other manufacturing parameters which may be affected by supplies and economic considerations in the supply market.